The invention relates to an arrangement for stabilizing a paper web in a paper machine or the like, in which the paper web is dried at least with the aid of cylinders and in which the paper web is kept supported towards the fabric in the area between the cylinders, i.e. in a pocket space, with the aid of a blow box. The invention relates also to a paper machine.
It is known to use blow boxes to support the web towards the fabric in the dryer section of a paper machine or the like, between the cylinders. In the publication U.S. Pat. No. 4,932,138 a blow box has been presented, which occupies almost the entire pocket space and in which there is a blow nozzle near the opening nip. No kind of an air guide between the lower cylinder and the blow box has been presented, except for the edge seals. In the publication U.S. Pat. No. 4,669,198 one solution using a big blow box is presented, which blow box has almost the size of the entire half of the pocket space, and in which there is one blow opening near the opening nip, and in the lower part, almost in a vertical direction in the upper part of the cylinder, a low air guide. The presented blow box is fairly big filling almost entirely the half of the pocket space. A big blow box is also fairly cumbersome for different purposes and expensive to manufacture. In the publication U.S. Pat. No. 6,115,938 a blow box placed in the packet space has been presented, in which blow box the supporting of the web towards the fabric has been arranged with the aid of a blow nozzle placed in the lower part of the blow box. In this structure the structures arranged in connection with the lower cylinder are, however, quite complicated and difficult to manufacture.
In the publication U.S. Pat. No. 6,189,232 a blow box has been presented from which the blow is directed towards the web so that the air flow coming along the web is prevented from drifting along with the web. A flexible wall that has been arranged in the vicinity of the blow nozzle is also presented in the publication. Moreover, in the publication seals are presented that have been arranged both on the inlet side and on the outlet side of the web so that from their other ends they are attached to the blow box and their other ends are in touch with the cylinder.
In the publication FI 110 442 a dryer section has been presented, which in its general outlines corresponds to the solution presented in the publication U.S. Pat. No. 6,189,232. In this publication, however, there is only one seal that has been arranged on the outlet side of the web. In both publications this seal is very small in dimension in relation to the dimensions of the blow box. The blow boxes are also carefully fitted in the pocket space remaining between the cylinders, in other words, their lower edges are curved following the configuration of the cylinder.
In the publication FI 76610 a solution has been presented, in which two blow boxes have been arranged in the pocket space between the cylinders. An auxiliary wall has been arranged in both blow boxes.
The problem of the above-mentioned solutions is that they need to be built separately for each paper machine, because in them the blow boxes are substantially of the same size and form as the pocket space remaining between the rolls or the cylinders.